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    <title>Document</title>
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    <script>
      Array.prototype.myMap = function (callback) {
        let arr = []
        for (let i = 0; i < this.length; i++) {
          arr[i] = callback(this[i], i, this)
        }
        return arr
      }

      const arr = [2, 3, 4, 5, 6, 7]
      let newArr = arr.myMap(function (item, index, array) {
        return item * 3
      })
      console.log(newArr)
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